The present invention generally relates to integrated circuits, and more particularly, to a system for preventing tampering of an integrated circuit.
Integrated circuits (ICs), such as those used in set-top boxes, engine control units (ECUs), and cryptographic systems, often store sensitive information including personal data, financial transaction authorization codes, security passwords, and secure session keys, and thus are prone to unauthorized access by hackers. A known technique used by hackers to gain access to information residing in an IC is micro-probing. Micro-probing involves forming an electrical contact with the IC by dropping fine-tipped probe needles directly on the point of interest of the IC, or on an area of the IC to which the point of interest is connected. The probe needles are held by a micro-manipulator that is controlled by the hacker to precisely land the probe needle on the IC.
To protect ICs from micro-probing, static wire-meshes have been designed that are placed close to the ICs. FIG. 1A is a schematic block diagram of a conventional static wire-mesh system 100. The static wire-mesh system 100 includes a conventional tamper detection module 102, a static wire-mesh 104, and first and second sets of wires 106 and 108. The first set of wires 106 includes a first wire segment 110 and the second set of wires 108 includes a second wire segment 112.
The first set of wires 106 is connected to a voltage supply (VDD) and to a low active tampering line of the tamper detection module 102, and the second set of wires 108 is connected to ground (GND) and to a high active tampering line of the tamper detection module 102. Wire segments associated with the first and second sets of wires 106 and 108, viz., the first and second wire segments 110 and 112, are placed in an alternating pattern to form the static wire-mesh 104 that protects an IC (not shown) from unauthorized access via probing. The wire segments 110, 112 are placed such that any two adjacent wire segments are at different potentials and spacing between adjacent wire segments is small enough to prevent a probe needle (not shown) from penetrating the static wire-mesh 104 without making contact with either of the wire segments. Contact of the probe needle with either of the wire segments causes the corresponding tampering lines, i.e., the high and low active tampering lines, to be activated, which in turn sets off a self-erase sequence that erases the sensitive information in the IC.
FIG. 1B is a schematic block diagram of the static wire-mesh system 100 after being altered to enable micro-probing. In addition to the elements depicted to be a part of FIG. 1A, the static wire-mesh system 100 includes first through fourth wire-connectors 114a-114d. FIG. 1B also shows a micro-probe 116 penetrating the wire mesh system 100.
The wire segments associated with the first set of wires 106 are shorted using the first and third wire-connectors 114a and 114c and the wire segments associated with the second set of wires 108 are shorted using the second and fourth wire-connectors 114b and 114d. A wire length between the first and third wire-connectors 114a and 114c and between the second and fourth wire-connectors 114b and 114d is cut to form a void large enough for an intrusion by the micro-probe 116. Since, the wire-segments are shorted, the conventional tamper detection module 102 does not detect the cutting of the wire segments and thus the intrusion by the micro-probe 116.
Although the static wire-mesh is efficient in thwarting direct micro-probing attempts, the static voltages used for detecting intrusions render the static wire-mesh vulnerable to being cut and easily bypassed. Further, since the wire segments are at constant potential, a hacker has a time for shorting and cutting the wire segments without activating the tampering lines and setting off the self-erase sequence.
Therefore, it would be advantageous to have a wire-mesh that does not use static voltages for micro-probe detection, that cannot be easily bypassed, and that overcomes the above-mentioned limitations of the conventional static wire-meshes.